Field
The disclosed embodiments relate to the design of a tunable laser. More specifically, the disclosed embodiments relate to the design of fast tunable hybrid laser that integrates a fast silicon micro-electromechanical systems (MEMS) optical switch with multiple III-V gain media and one or more banks of reflective silicon optical filters.
Related Art
Energy-efficient and cost-effective switches are important building blocks for communication networks in data centers and high-performance computing systems. Existing three-dimensional MEMS-based photonic switches can provide low-cost and energy-efficient traffic switching. However, the millisecond switching times of such switches limit their application to either “elephant” traffic with large packet sizes, or network reconfigurations that are not sensitive to switching time. Recently developed silicon-photonic switches can potentially provide fast optical circuit switching with microsecond, or even nanosecond response times. Moreover, relatively large-scale integrated photonic switches can be realized on silicon using MEMS-actuated matrices. However, existing silicon-photonic MEMS-based optical switches support single polarization only, making them undesirable for practical deployment in optical networks.
An alternative to the optical-switching approach is to use the unique wavelength routing capability of arrayed-waveguide-grating-routers (AWGRs) and carrier wavelength switching at the source node. However, a wavelength-tunable laser source is needed for such source-originated optical switching. A wavelength-tunable hybrid laser source has been implemented using back-end-of-the-line (BOEL) hybrid integration of a III-V gain chip with a silicon-on-insulator (SOI) photonic chip with a tunable wavelength selective reflector. (See Jin-Hyoung Lee, Jock Bovington, Ivan Shubin, Ying Luo, Jin Yao, Shiyun Lin, John E. Cunningham, Kannan Raj, Ashok V. Krishnamoorthy and Xuezhe Zheng, “Demonstration of 12.2% wall plug efficiency in uncooled single mode external-cavity tunable Si/III-V hybrid laser,” Optics Express, 23(9) 12079-12088, 2015.) Unfortunately, the wavelength tuning speed of this type of silicon-assisted hybrid laser is limited by the response time of the silicon thermal tuner, which is usually on the order of a few microseconds.
Hence, to achieve the goal of sub-microsecond optical switching, faster tunable lasers are needed.